Mesh support assembly for a pickup tube



Dec. 18, 1962 B. ANTONIADES MESH SUPPORT ASSEMBLY FOR A PICKUP TUBE Filed April 19, 1961 JNVENTOR, BASIL ANTON/A055.

A TTQRNE )1 States States of America as represented by the Secretary of the Army Filed Apr. 19, 1961, Ser. No. 104,189 4 Claims. (Cl. 313-848) This invention relates to a mesh support assembly for a pickup tube such as used in television cameras and the like, and more particularly to a snap-in mesh support as sembly that is electrically isolated from the wall electrode of the pickup tube.

In the prior art, certain photoconductive pickup tubes are well known. One tube of this type is known as the Vidicon. In this tube, a photoconductor is placed on a transparent signal plate. One side of the photoconductor is exposed to the light from the scene that is to be reproduced and the other side is scanned through a fine wire mesh electrode by an electron beam. The light from the scene develops a charge pattern on the photoconductor. The electron scanning beam discharges the charge pattern and develops an output signal on the signal plate.

In prior art Vidicon tubes, the wall electrode and the mesh electrode are electrically and physically tied together internally, and therefore, the wall electrode and the mesh electrode are operated at the same potential. Op crating these two elements at the same potential may cause a bunching of secondary electrons at the mesh electrode. The secondary electrons set up a space charge that causes undesirable beam splitting. It has been found that the tube will still operate properly if the wall electrode and mesh are operated at slightly different potentials. By so operating these elements at different potentials the secondary electrons are swept out, thereby, preventing beam splitting that might otherwise occur.

Other problems besides the undesirable beam splitting mentioned above have been encountered with prior art Vidicon tubes. For example, the complicated structure of these tubes is not conducive to rapid and inexpensive manufacture of the tubes. Also, the known manufacturing processes have not prevented contamination of the mesh and photoconductor by such things as dust particles.

It is, therefore, an object of this invention to provide a new and improved pickup tube wherein the wire mesh and the wall electrode are electrically isolated.

Another object of this invention is to provide means to operate the mesh and wall electrodes at separate potentials.

A still further object of this invention is to provide a novel mesh support assembly that affords protection against contamination of the mesh screen and the photoconductor during assembly of the tube.

These and other objects of the invention will be readily apparent by referring to the following specification and accompanying drawing in which like parts in various figures have like number and in which:

FIG. 1 is a cross-sectional view of a pickup tube in accordance with this invention.

FIG. 2 is a top View of the mesh ring.

FIGS. 3A and 3B are top and side views, respectively, of the mesh support ring.

FIGS. 4A and 4B are top and side views, respectively, of the mesh support clamp.

FIG. 5 is a side view of the complete mesh assembly.

FIG. 6 is a top View of the mesh contact ring.

The pickup tube 10, constructed in accordance with this invention, is shown in FIG. 1 as comprising an evacuated glass envelope 11 having an electron gun and various electrodes 13 in one end thereof, and a target electrode 14 at the other end of the envelope.

As target electrode 14, the electron gun and electrodes atent 0 3,069,586 Patented Dec. 18, 1962 13 are conventional, no further discussion of these elements is deemed necessary. A cylindrical wall electrode 12 extends nearly the entire length of the envelope and is connected at one end to one of the pins 20. A contact ring 17 having a small protrusion or lug 24 on the outer circumference is spaced slightly from the end of wall electrode 12. The envelope, before assembly, actually consists of two sections, a lower bulb section 23 and an upper bulb section 22. Contact ring 17, not including lug 24, has an outer diameter slightly larger than the inside diameter of the envelope. The inner diameter of the ring is sufliciently smaller than the inner diameter of the envelope to provide a mounting flange or ledge for anchoring the mesh support assembly described below. Contact ring 17 is placed on top of the lower bulb section 23 and the upper bulb section 22 is then sealed to the lower bulb section, to hold the contact ring in place. Lug 24 protrudes beyond the outer surface of the envelope. As will become apparent later in this specification lug 24 is used to supply an operating potential to mesh electrode 15. Wire mesh electrode 15 is supported by a snap-in assembly 21 made up of components numbered 16 through 19. This assembly and its component parts are shown in greater detail in FIGS. 2 through 5.

Snap-in mesh assembly 21 consists of a ring 16; wire mesh electrode 15; a cylindrical mesh support ring 19 having a flange 25 on one end of the cylinder; and a support clamp 18 that has a hollow cylindrical base portion 27 and a series of spring clips 26 integral with base 27. The cylindrical base 27 of the support clamp is split longitudinally to facilitate insertion of mesh support ring 19 during assembly of these parts.

The mesh 15 placed on top of flange 25 of support ring 19, and ring 16 is placed thereover. These are bonded together to hold the mesh in proper position. Support ring 19 is then placed inside the support clamp 18 and bonded to the base portion 27 of said clamp to form the complete snap-in mesh assembly shown in FIG. 5. The mesh assembly is then snapped inside mesh contact ring 17 and held in position by spring clips 26 expanding outwardly beneath ring 17. The contact ring and all of the components of the napin assembly are made of conductive materials. It is thus apparent that an operating potential can be applied to the mesh electrode by means of lug 24.

Briefly, manufacturing steps of interest in this invention are as follows: Mesh contact ring 17 is placed on top of lower bulb section 23 of envelope 11. Upper bulb section 22 is then sealed to the lower bulb section; holding the mesh contact ring securely in position in the wall of the tube.

Snap-in mesh assembly 21 is then pressed through contact ring 17 until spring clips 26 snap outward beneath mesh contact ring 17 to lock the mesh assembly in place. The final step of assembly is the sealing of target electrode 14 and associated elements in the free end of the upper bulb section 22.

From the foregoing it is apparent that the mesh snap-in assembly in accordance with this invention is easily manufactured, and provides means to apply separate operating potentials to the wall electrode and the mesh electrode to prevent beam splitting. Also, due to the fact that the mesh electrode and the target electrode are placed in position in the last stages of assembly it is possible to keep the mesh and the target free from contamination during the manufacturing process.

What is claimed is:

1. A photoconductor pickup tube comprising an evacuated envelope having an upper and lower bulb section; an electron gun positioned in one end of said lower bulb section; a hollow tubular electrode within said lower bulb section; a first ring element sealed between said upper and lower bulb sections; a second ring element; a flanged cylindrical support ring; a mesh electrode bonded between said second ring element and said flanged support ring; a support clamp having a cylindrical base portion and a plurality of spring clips integral with said base portion; said base portion being bonded to said support ring and said spring clips being press-fitted into said first ring element; means to apply a first electric potential to said tubular electrode; and means to apply a second electric potential to said first ring element.

2. A photoconductor tube as defined in claim 1 wherein said last named means comprises a small protrusion integral with and extending beyond the outer circumference of said first ring element, said protrusion extending beyond the outer surface of said envelope.

3. A photoconductive pickup tube comprising an evacuated envelope having upper and lower bulb sections; a tubular electrode within said lower bulb section; a first ring sealed between said upper and lower bulb sections; a support clamp having a hollow cylindrical base portion and spring clips integral with said base portion press-fitted into said first ring; a support element bonded at one end to the base portion of said support clamp; a mesh electrode bonded to the other end of said support element; a second ring bonded to said mesh electrode; means to apply an electric potential to said tubular electrode; and means to apply another electric potential to said mesh electrode.

4. The photoconductor pickup tube as defined in claim 3, wherein said means to apply a potential to said mesh electrode comprises a protrusion integral with a part of the outer circumference of said first ring and extending beyond the outer surface of said envelope.

References Cited in the file of this patent UNITED STATES PATENTS 2,843,772 Weimer July 15, 1958 2,894,163 Orthuber et a1. July 7, 1959 2,951,962 Miller et a1. Sept. 7, 1960 van 

